Editing Invincible-class battlecruiser (section)

===Fire control===
The spotting tops at the head of the fore and main masts controlled the fire of the ''Invincible''s' main guns. Data from a {{convert|9|ft|m|adj=on|1}} [[Barr and Stroud]] [[Rangefinding telemeter|rangefinder]] was input into a [[Dumaresq]] mechanical computer and electrically transmitted to [[Vickers range clock]]s located in the Transmitting Station located beneath each spotting top where it was converted into range and deflection data for use by the guns. The target's data was also graphically recorded on a plotting table to assist the gunnery officer in predicting the movement of the target. Each gun turret had its own transmission equipment and the turrets, Transmitting Stations, and spotting tops could be connected in almost any combination. Firing trials against {{HMS|Hero|1885|2}} in 1907 revealed this system's vulnerability to gunfire as the spotting top was hit twice and a large splinter severed the [[Speaking tube|voice pipe]] and all wiring running along the mast. To guard against this possibility, 'A' turret was fitted, during refits between 1911 and 1914, with a 9-foot rangefinder at the rear of the turret roof and it was equipped to control the entire main armament.<ref>Roberts, pp. 90–91</ref>

Fire control technology advanced quickly during the years immediately preceding World War I and the development of the [[Frederic Charles Dreyer#Dreyer Fire Control Table|Dreyer Fire Control Table]] was one such advance. It combined the functions of the Dumaresq and the range clock and a simplified version, the Mk I, was fitted to the ''Invincible''s during refits in 1915–16. The more important development was the director firing system. This consisted of a [[Fire-control system#Naval fire control|fire control director]] mounted high in the ship which electrically provided gun data to the turrets via pointers, which the turret crewmen only had to follow. The director officer fired the guns simultaneously, which aided in spotting the shell splashes and minimised the effects of the roll on the dispersion of the shells. ''Invincible'' was the first battlecruiser to receive this system during her refit from April to August 1914, but its installation was interrupted by the outbreak of the war and it was not fully working until after the [[Battle of the Falkland Islands]] in November. ''Indomitable'' and ''Inflexible'' didn't receive their systems until May 1916, immediately before the [[Battle of Jutland]].<ref>Roberts, pp. 92–93</ref>